Hybrid workpiece joining

ABSTRACT

A joining device includes a nose, a punch, and a die anvil. The punch is coaxially slidable within the nose. A fastener is arranged within the nose and is coaxially slidable within the nose and movable by the punch. An ultrasonic vibration is focused through the die anvil to a zone on a material assembly arranged thereon for heating the zone. The punch is configured to drive the fastener outwardly from the nose and into the material assembly at the zone.

FIELD

The present disclosure relates to a workpiece assembly including a fastener and a joining method thereof.

INTRODUCTION

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Joining of both ferrous and non-ferrous materials can be achieved through various methods. In one example for joining overlapping members, a self-piercing rivet can be driven under pressure into the members. A die or mandrel may disrupt a terminal end of the self-piercing rivet in order to create a mechanical interference between the members and the rivet. In another example for joining overlapping members, an ultrasonic welding device can use high-frequency ultrasonic vibrations to generate heat at an interface of the workpieces. The heated workpieces may melt sufficiently to create a joint at the interface.

SUMMARY

A joining device includes a nose, a punch, and a die anvil. The punch is coaxially slidable within the nose. A fastener is arranged within the nose and is coaxially slidable within the nose and movable by the punch. An ultrasonic vibration is focused through the die anvil to a zone on a material assembly arranged thereon for heating the zone. The punch is configured to drive the fastener outwardly from the nose and into the material assembly at the zone.

In some embodiments, the material assembly includes a first and second workpiece and the fastener is configured to join the first workpiece to the second workpiece. The fastener further includes a head and a shank extending from the head, and the punch may contact the fastener at the head and drive the shank through the first workpiece and into the second workpiece. Furthermore, the die anvil has a die face that receives the second workpiece when the shank of the fastener is in the zone, and the shank of the fastener is deformed to create a mechanical joint with the first and second workpieces. Additionally, at least a portion of the zone on the material assembly is fused upon cooling of the zone.

A joining device includes a nose horn, a punch coaxially slidable within the nose horn, and a die having a material assembly arranged thereon. A fastener is arranged within the nose horn and is coaxially slidable within the nose horn and movable by the punch. The nose horn is axially movable to a position contacting the material assembly. An ultrasonic vibration is focused through the nose horn to a zone on the material assembly for heating the zone. The punch is configured to drive the fastener outwardly from the nose horn and into the material assembly at the zone.

In some embodiments, the material assembly includes a first and second workpiece and the fastener is configured to join the first workpiece to the second workpiece. The fastener further includes a head and a shank extending from the head, and the punch may contact the fastener at the head and drive the shank through the first workpiece and into the second workpiece. Furthermore, the die has a die face that receives the second workpiece when the shank of the fastener is in the zone, and the shank of the fastener is deformed to create a mechanical joint with the first and second workpieces. Additionally, at least a portion of the zone on the material assembly is fused upon cooling of the zone.

A joining device includes a nose, a punch, and an electrode die. The punch is coaxially slidable within the nose. A fastener is arranged within the nose and is coaxially slidable within the nose and movable by the punch. An electrical current is focused through the electrode die to a zone on a material assembly arranged thereon for heating the zone. The punch is configured to drive the fastener outwardly from the nose and into the material assembly at the zone.

In some embodiments, the electrode die includes an insulator (e.g., ceramic or polymer), a first conductor (e.g., tungsten carbide) arranged about the insulator, and a second conductor (e.g., steel) arranged on an end surface of the first conductor, with the second conductor configured to contact the material assembly. The material assembly can include a first and second workpiece with the fastener configured to join the first workpiece to the second workpiece. The fastener further includes a head and a shank extending from the head, and the punch may contact the fastener at the head and drive the shank through the first workpiece and into the second workpiece. Additionally, at least a portion of the zone on the material assembly is fused upon cooling of the zone. Furthermore, the shank of the fastener is deformed to create a mechanical joint with the first and second workpieces. In addition, an electrical power source can be interconnected with the electrode die to selectively create an electrical circuit for conducting electrical current through the first and second conductors, where the electrical current at the second conductor locally heats the second workpiece.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIGS. 1A through 1E depict schematic views of an exemplary hybrid joining machine according to the present disclosure;

FIG. 2 is a flow diagram of an exemplary hybrid joining process utilizing the hybrid joining machine of FIGS. 1A through 1E;

FIGS. 3A through 3E depict schematic views of another exemplary hybrid joining machine according to the present disclosure;

FIG. 4 is a flow diagram of another exemplary hybrid joining process utilizing the hybrid joining machine of FIGS. 3A through 3E;

FIGS. 5A through 5E depict schematic views of yet another exemplary hybrid joining machine according to the present disclosure; and

FIG. 6 is a flow diagram of yet another exemplary hybrid joining process utilizing the hybrid joining machine of FIGS. 5A through 5E.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Further, directions such as “top,” “side,” “back”, “lower,” and “upper” are used for purposes of explanation and are not intended to require specific orientations unless otherwise stated. These directions are merely provided as a frame of reference with respect to the examples provided, but could be altered in alternate applications.

The present disclosure describes a hybrid technique for joining workpieces, such as polymeric composites, by a combination of integral fastening (e.g., self-piercing riveting) and localized material fusing. With reference to the drawings, wherein like reference numbers refer to like components, each of the exemplary hybrid joining machines includes a nose 12, a punch 14, and a die 16. The hybrid joining machines can be used to join first and second workpieces 18, 20 with a fastener 22. In one exemplary embodiment, the fastener 22 can be a rivet having a head portion 24 and a generally cylindrical hollow shank 26 ending in a tapered extremity 28. The rivet 22 is configured to mechanically fasten the first and second workpieces 18, 20 when subjected to a driving force, such as may be achieved by the punch 14 acting on the rivet 22. The rivet 22 is referred to as a “self-piercing” rivet, as the tapered extremity 28 is sufficient to cause penetration of the workpieces 18, 20 under the force of the punch 14. Furthermore, the shank 26 is configured to deform to create a mechanical joint without requiring a lead hole for the rivet 22 in the workpieces 18, 20.

With reference now to FIGS. 1A through 1E, an exemplary hybrid joining machine 10 incorporates a hybrid joining technique involving the mechanical fastening of riveting with an ultrasonic energy applied to the second workpiece 20. In this regard, line power (e.g., low-frequency electrical signal of about 50-60 Hz) is converted to a high frequency, high voltage electrical signal (e.g., 15-70 kHz, and more particularly 20-40 kHz). The high frequency electrical signal is then converted to a mechanical vibration at an ultrasonic frequency in a converter (i.e., transducer). An optional booster may be included in the system in order to amplify the mechanical vibration such that the vibration amplitude can be increased. The ultrasonic vibrations then propagate through the die anvil 16. An end face 30 of the die anvil 16 can then focus the ultrasonic vibration and deliver the vibration energy to a specified area on a material (e.g., at a portion of the second workpiece 20 to be riveted).

With reference to FIG. 2, a method 50 of joining the workpieces 18, 20 will be described with respect to the hybrid joining machine 10 of FIGS. 1A through 1E. Specifically, at step 52, first and second workpieces 18, 20 are arranged on the die anvil 16 such that the second, lower workpiece 20 rests directly on the die anvil 16 and the first, upper workpiece 18 rests on the lower workpiece 20, as shown in FIG. 1A. At step 54, the nose 12 is actuated by hydraulic pressure so as to behave as a retractable clamping cylinder for the machine 10. The nose 12 is driven downwardly towards the upper workpiece 18 to urge the workpieces 18, 20 against the die anvil 16, as shown in FIG. 1B. It should be noted that other drive mechanisms may be used for driving the nose 12, e.g., an electrically powered screw assembly, an electrically powered actuator, or via a spring.

At step 56, the die anvil 16 is excited with ultrasonic vibration so as to locally heat the workpieces 18, 20. The transmitted waves are bounced back by the die anvil 16. The mechanical waves from the vibration cause the workpieces 18, 20 to oscillate (i.e., deform). The oscillations of the workpieces 18, 20 generate heat at the both the interface between the die anvil 16 and workpiece 20 and at the interface between the workpieces 18, 20 creating a localized heated material zone 32. At step 58, the punch 14, which is coaxially slidable within the nose 12, is actuated so as to drive the rivet 22 into the upper workpiece 18 (see FIG. 1C). The punch 14 continues driving the rivet 22 until the rivet 22 penetrates the lower workpiece 20. In particular, the punch 14 contacts the head portion 24 and pierces the upper workpiece 18 with the shank 26 only partially piercing and entering, but not completely passing through the lower workpiece 20 (i.e., does not pass through the bottom surface of the lower workpiece 20). Notably, the localized heated material zone 32 allows for enhanced riveting since stresses and friction in this material zone are reduced.

At step 60 (see FIG. 1D), the shank 26 and the material of the lower workpiece 20 immediately adjacent to the shank 26 are then deformed through interaction with the die anvil 16. The bottom surface of the lower workpiece 20 is subjected to the force of the die anvil 16 as described herein such that the shape of the surface of the lower workpiece 20 is modified to conform to the shape of the die anvil 16. The complementary shape on the lower workpiece 20 mechanically interlocks the workpieces 18, 20.

Furthermore, as the localized heated material zone 32 cools, a fused region 34 is created at an interface between the workpieces 18, 20. In this way, the mechanical joint is supplemented by the fused region 34 between the upper and lower workpieces 18, 20. The fused region 34 contributes to the strength of the mechanical interface. The fused region 34 is most conveniently achieved if both the workpieces 18, 20 are thermoplastic composite materials, having similar melting temperatures. However, the workpieces 18, 20 may be alternate materials, including materials different from one another provided they are weldably compatible. The fused region 34 should be considered representative of a wide range of fused areas that may result from this process. Depending on the duration and magnitude of application of the ultrasonic vibration, the extent of fused region 34 may vary. However, to strengthen the interface and ease the insertion of the rivet 22, at least a minimum localized heated material zone 32 should be developed around the circumference of shank 26.

At step 62, the punch 14 and nose 12 are withdrawn from the riveted workpieces 18, 20 and the riveted workpieces 18, 20 are removed from the die anvil 16 (see FIG. 1E). The assembled workpieces 18, 20 and rivet 22 provide a robust weld, capable of withstanding delamination and microcracking.

With reference now to FIGS. 3A through 3E, an exemplary hybrid joining machine 100 incorporates a hybrid joining technique involving the mechanical fastening of riveting with an ultrasonic energy applied to a workpiece. As previously noted, line power (e.g., low-frequency electrical signal of about 50-60 Hz) is converted to a high frequency, high voltage electrical signal (e.g., 15-70 kHz, and more particularly 20-40 kHz). The high frequency electrical signal is then converted to a mechanical vibration at an ultrasonic frequency in a converter (i.e., transducer). An optional booster may be included in the system in order to amplify the mechanical vibration such that the vibration amplitude can be increased. The ultrasonic vibrations then propagate through a nose horn 112. An end face 136 of the nose horn 112 can then focus the ultrasonic vibration and deliver the vibration energy to a specified area on a material (e.g., at a portion of a first workpiece 118 to be riveted).

With reference to FIG. 4, a method 150 of joining first and second workpieces 118, 120 will be described with respect to the hybrid joining machine 100 of FIGS. 3A through 3E. Specifically, at step 152, the first and second workpieces 118, 120 are arranged on a die 116 such that the second, lower workpiece 120 rests directly on the die 116 and the first, upper workpiece 118 rests on the lower workpiece 120, as shown in FIG. 3A. At step 154, the nose horn 112 is actuated by hydraulic pressure so as to behave as a retractable clamping cylinder for the machine 100. The nose horn 112 is driven downwardly towards the upper workpiece 118 to urge the workpieces 118, 120 against the die 116, as shown in FIG. 3B. It should be noted that other drive mechanisms may be used for driving the nose horn 112, e.g., an electrically powered screw assembly, an electrically powered actuator, or via a spring.

At step 156, the nose horn 112 is excited with ultrasonic vibration so as to locally heat the workpieces 118, 120. The mechanical waves from the vibration cause the workpieces 118, 120 to oscillate (i.e., deform). The oscillations of the workpieces 118, 120 generate heat at both the interface between the nose horn 112 and the workpiece 118 and at the interface between the workpieces 118, 120 creating a localized heated material zone 132. At step 158, a punch 114, which is coaxially slidable within the nose horn 112, is actuated so as to drive a rivet 122 into the upper workpiece 118. The punch 114 continues driving the rivet 122 until the rivet 122 penetrates the lower workpiece 120 (see FIG. 3C). In particular, the punch 114 contacts a head portion 124 of the rivet 122 and pierces the upper workpiece 118 with a shank 126 of the rivet 122 only partially piercing and entering, but not completely passing through the lower workpiece 120 (i.e., does not pass through the bottom surface of the lower workpiece 120). Notably, the localized heated material zone 132 allows for enhanced riveting since stresses and friction in this material zone are reduced.

At step 160, the shank 126 and the material of the lower workpiece 120 immediately adjacent to the shank 126 are deformed through interaction with the die 116. The bottom surface of the lower workpiece 120 is subjected to the force of the die 116 as described herein such that the shape of the surface of the lower workpiece 120 is modified to conform to the shape of the die 116. The complementary shape on the lower workpiece 120 mechanically interlocks the workpieces 118, 120, as shown in FIG. 3D.

Furthermore, as the localized heated material zone 132 cools, a fused region 134 is created at an interface between the workpieces 118, 120. In this way, the mechanical joint is supplemented by the fused region 134 between the upper and lower workpieces 118, 120. The fused region 134 contributes to the strength of the mechanical interface. The fused region 134 is most conveniently achieved if both the workpieces 118, 120 are thermoplastic composite materials, having similar melting temperatures. However, the workpieces 118, 120 may be alternate materials, including materials different from one another provided they are weldably compatible. The fused region 134 should be considered representative of a wide range of fused areas that may result from this process. Depending on the duration and magnitude of application of the ultrasonic vibration, the extent of the fused region 134 may vary. However, to strengthen the interface and ease the insertion of the rivet 122, at least a minimum localized heated material zone 132 should be developed around the circumference of shank 126.

At step 162, the punch 114 and nose 112 are withdrawn from the riveted workpieces 118, 120 and the riveted workpieces 118, 120 are removed from the die 116 (see FIG. 3E). The assembled workpieces 118, 120 and rivet 122 provide a robust weld, capable of withstanding delamination and microcracking.

With reference now to FIGS. 5A through 5E, an exemplary hybrid joining machine 200 incorporates a hybrid joining technique involving the mechanical fastening of riveting with an electrode energy (i.e., Joule heat) applied to a workpiece. In this regard, an electrical power source may be connected to a die to create an electrical circuit that generates heat at a specified area on a material (e.g., at a portion of a workpiece to be riveted).

In particular, a lower electrode die 216 may be split into a first portion 238, also referred to as an insulator (e.g., polymer, ceramic); a second portion 240, also referred to as a first conductor (e.g., tungsten carbide); and a washer 242, also referred to as a second conductor (e.g., steel). The insulator 238 may be formed with the first conductor 240 to establish an interior wall 244 of the die 216. The second conductor 242 may be arranged on an end surface 230 of the first conductor 240 so as to contact a lower workpiece 220. An electrical power source 246 may be interconnected with the die 216 at the first conductor 240, in order to selectively create an electrical circuit. The electrical circuit runs through the electrically conducting components of the assembly, namely from the first conductor 240 through the second conductor 242 and out again through the first conductor 240. The electrical energy running through the second conductor 242 locally heats the lower workpiece 220.

With reference now to FIG. 6, a method 250 of joining workpieces 218, 220 will be described with respect to the hybrid joining machine 200 of FIGS. 5A through 5E. Specifically, at step 252, first and second workpieces 218, 220 are arranged on the die 216 such that the second, lower workpiece 220 rests directly on the die 216 and the first, upper workpiece 218 rests on the lower workpiece 220, as shown in FIG. 5A. At step 254, the nose 212 is actuated by hydraulic pressure so as to behave as a retractable clamping cylinder for the machine 200. The nose 212 is driven downwardly towards the upper workpiece 218 to urge the workpieces 218, 220 against the die 216, as shown in FIG. 5B. It should be noted that other drive mechanisms may be used for driving the nose 212, e.g., an electrically powered screw assembly, an electrically powered actuator, or via a spring.

At step 256, the electrical power source 246 is initiated and electrical current flows through the first conductor 240 to the second conductor 242, around the second conductor 242, and back out through the opposite side of the first conductor 240, as depicted by arrows 248. The electrical current passing through the second conductor 242 locally generates joule heat, consequently heating the workpieces 218, 220. The heat may propagate through the workpiece 220 creating a localized heated material zone 232.

At step 258, a punch 214, which is coaxially slidable within the nose 212, is actuated so as to drive a rivet 222 into the upper workpiece 218. The punch 214 continues driving the rivet 222 until the rivet 222 penetrates the lower workpiece 220 (see FIG. 5C). In particular, the punch 214 contacts a head portion 224 of the rivet 222 and pierces the upper workpiece 218 with a shank 226 of the rivet 222 only partially piercing and entering, but not completely passing through the lower workpiece 220 (i.e., does not pass through the bottom surface of the lower workpiece 220). Notably, the localized heated material zone 232 allows for enhanced riveting since stresses and friction at least in this material zone are reduced.

At step 260, the shank 226 and the material of the lower workpiece 220 immediately adjacent to the shank 226 are deformed through interaction with the die 216. The bottom surface of the lower workpiece 220 is subjected to the force of the die 216 as described herein such that the shape of the surface of the lower workpiece 220 is modified to conform to the shape of the die 216. The complementary shape on the lower workpiece 220 mechanically interlocks the workpieces 218, 220, as shown in FIG. 5D. The electrical current from the electrical power source 246 may then be removed in order to allow the material zone 232 to cool. As previously noted, to ease the insertion of the rivet 222, at least a minimum localized heated material zone 232 should be developed around the circumference of shank 226.

At step 262, the punch 214 and nose 212 are withdrawn from the riveted workpieces 218, 220 and the riveted workpieces 218, 220 are removed from the die 216 (see FIG. 5E). The assembled workpieces 218, 220 and rivet 222 provide a robust weld, capable of withstanding delamination and microcracking.

Embodiments of the present disclosure are described herein. This description is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for various applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 

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 6. A joining device comprising: a nose horn; a punch coaxially slidable within the nose horn; a fastener arranged within the nose horn, the fastener being coaxially slidable within the nose horn and movable by the punch; and a die having a material assembly arranged thereon, wherein the nose horn is axially movable to a position contacting the material assembly, wherein an ultrasonic vibration is focused through the nose horn to a zone on the material assembly for heating the zone, and wherein the punch is configured to drive the fastener outwardly from the nose horn and into the material assembly at the zone.
 7. The joining device of claim 6, wherein the material assembly includes a first and second workpiece and wherein the fastener is configured to join the first workpiece to the second workpiece.
 8. The joining device of claim 7, wherein the fastener further includes a head and a shank extending from the head, and wherein the punch contacts the fastener at the head and drives the shank through the first workpiece and into the second workpiece.
 9. The joining device of claim 8, wherein the die has a die face that receives the second workpiece when the shank of the fastener is in the zone, and wherein the shank of the fastener is deformed to create a mechanical joint with the first and second workpieces.
 10. The joining device of claim 6, wherein at least a portion of the zone on the material assembly is fused upon cooling of the zone.
 11. A joining device comprising: a nose; a punch coaxially slidable within the nose; a fastener arranged within the nose, the fastener being coaxially slidable within the nose and movable by the punch; and an electrode die, wherein an electrical current is focused through the electrode die to a zone on a material assembly arranged thereon for heating the zone, and wherein the punch is configured to drive the fastener outwardly from the nose and into the material assembly at the zone.
 12. The joining device of claim 11, wherein the electrode die further comprises: an insulator; a first conductor arranged about the insulator; and a second conductor arranged on an end surface of the first conductor, the second conductor configured to contact the material assembly.
 13. The joining device of claim 12, wherein the insulator is one of a ceramic and a polymer.
 14. The joining device of claim 12, wherein the first conductor is a tungsten carbide.
 15. The joining device of claim 12, wherein the second conductor is a steel.
 16. The joining device of claim 11, wherein the material assembly includes a first and second workpiece and wherein the fastener is configured to join the first workpiece to the second workpiece.
 17. The joining device of claim 16, wherein the fastener further includes a head and a shank extending from the head, and wherein the punch contacts the fastener at the head and drives the shank through the first workpiece and into the second workpiece.
 18. The joining device of claim 17, wherein at least a portion of the zone on the material assembly is fused upon cooling of the zone.
 19. The joining device of claim 17, wherein the shank of the fastener is deformed to create a mechanical joint with the first and second workpieces.
 20. The joining device of claim 16, wherein an electrical power source is interconnected with the electrode die to selectively create an electrical circuit for conducting electrical current through the first and second conductors, wherein the electrical current at the second conductor locally heats the second workpiece. 